Method for the manufacture of a quasi-homogeneous formation

ABSTRACT

A method of manufacturing a quasi-homogeneous formation from a plurality of separate particles of different size. The particles are separated into fractions according to size, which fractions together are required for filling a certain container volume. The amount of each fraction is determined so that when the particles are within the container, the smaller particles will fill out the hollow space between the larger particles. The determined amounts of all fractions are divided into several partial amounts in regularly distributed arrangement. Thereafter the uppermost particle layer, to avoid decomposition, is loaded by a pressure force, and the container is exposed to a vibration to reduce the spaces between the particles thereby creating a quasi-homogeneous formation.

Aug. 21,1973 G. PRANTL ETAL 3,754,059

METHOD FOR THE MANUFACTURE OF A QUASI-HOMOGENEOUS FORMATION Filed June 12. 1970 '.OAQAA MKM/W@ United States Patent Oliice 3,754,059 Patented Aug. 2l, 1973 3,754,059 METHOD FOR THE MANUFACTURE F A QUASI-HOMOGENEOUS FORMATION Gustav Prantl, Brugg, and Istvan Horvath, Wettingen, Switzerland, assignors to Gesellschaft zur Forderung der Forschung an der Eidg. Techn. Hochschule, Zurich, Switzerland Filed June 12, 1970, Ser. No. 45,628 Claims priority, application Switzerland, .lune 20, 1969, 9,408/ 69 Int. Cl. G21c 21/04 U.S. Cl. 264-.5 2 Claims ABSTRACT 0F THE DISCLOSURE A method of manufacturing a quasi-homogeneous formation from a plurrality of separate particles of different size. The particles are separated into fractions according to size, which fractions together are required for filling a certain container volume. The amount of each fraction is determined so that when the particles are within the container, the smaller particles will till out the hollow space between the larger particles. The determined amounts of all fractions are divided into several partial amounts. The container is then filled with the partial amounts in regularly distributed arrangement. Thereafter the uppermost particle layer, to avoid decomposition, is loaded by a pressure force, and the container is exposed to a vibration to reduce the spaces between the particles, thereby creating a quasi-homogeneous formation.

a rule, ceramic particles, for example uranium oxides orl plutonium oxides or carbides are used. These elements must illustrate a quasi-homogeneous and compact formation whereby the term quasi-homogeneous is supposed to characterize the quality of the formation which is the same all over except for the particle-shaped structure, for which reason it is necessary to put together particles of different size in such a manner that possibly no hollow spaces remain between them. For this purpose the particles are exposed to a vibration. In using this technique different methods are known. In one of these methods particles of a certain size are compressed in a container by means of vibration and the thus compressed particles then are prevented from a further movement by pressing a sieve against the free surface of the particles, the mesh width of said sieve being smaller than the particles themselves in order to be able to introduce through a renewed use of vibration particles of a smaller size through said sieve which particles are supposed to fill the hollow spaces between the larger particles. However, it is disadvantageous in this lknown method that only small round balls are suitable as particles, however, particles with broken edges, as they are often present in the case of ceramic materials for the here mentioned purpose, cannot be used. As a further disadvantage this method also becomes more difficult in the case of a very long container which mostly is a pipe since the smaller particles on the long path through the gross grid of the greater fraction tend to form bridges and to block the passages. Thus in the case of a very long container, the vibration time could only be extended considerably in order to overcome the mentioned effects which would have negative effects in the case of a mass produced process.

In a further llcnown method, the particles of the different fractions separated according to sizes are filled simultaneously into the container in exact quantity selection and are mixed when they meet in the container for which, however, extremely expensive dosing devices are needed which make the method disadvantageously expensive.

The invention pursues the goal of a considerable method specification particularly in order to thereby have the possibility to use both ball-shaped particles and particles with breaking edges for the manufacture of a quasihomogeneous formation.

The method of the above-mentioned type is therefore characterized according to the invention in such a manner that the fractions of particles are separated according to sizes and which together are required for the formation of a certain container volume, the amount of each fraction is determined according to the measure that within the container volume the next smaller particles lill out the hollow spaces between the larger particles, and that the thus determined amounts of all fractions are each divided into equally many partial amounts and are brought through an interchangeable filling of the partial amounts into the container into an arrangement regularly ydistributed over the container volume, whereafter the uppermost particle layer, to avoid a decomposition, is loaded by a pressure force and the container is exposed to a Vibration in such a manner that, by reducing the spaces between the particles, a quasi-homogeneous formation is created.

The partial amounts of different fractions can be advantageously filled successively into the container whereby the sequence is repeated according to the number of divisions of each fraction. lf for example each fraction is divided into four partial amounts, then in the case of three present fractions of different size the sequence of these fractions will be repeated four times. The individual partial amounts of the fractions can thereby preferably succeed one another in the sequence of decreasing size. It is also possible to lill mixed partial amounts of different fractions, interchangeably with a partial amount of a further fraction into the container whereby this is also repeated corresponding to the number of divisions of each of the fractions. The optimum layer height of a partial amount in the container is advantageously determined according to the provided particle quality in view of the shortest vibration time and the number of divisions of the fraction required for a requested total length of the formation can be found with the layer height determined in such a manner.

Exemplary embodiments of the method of the invention are discussed hereinafter in connection with a drawing which schematically illustrates the different layering possibilties for the partial amounts of the fractions.

In the drawing:

FIG. l is a longitudinal cross-sectional view of a container filled with particles, into which container according to the method three fractions of different sizes each with a division into four partial amounts are filled interchangeably.

'F.IG. 2 illustrates a container filled with particles, into which container two mixed partial amounts of different fractions are filled interchangeably with a partial amount of a further fraction.

According to FIG. 1 a container 1 is arranged on a vibrator 2. Particles of three fractions of different sizes are filled into the container 1, whereby each fraction is divided into four equal partial amounts, namely a coarse .fraction 3, a medium fraction 4 and a line fraction 5. Each ne fraction 5 is followed by a coarse fraction 3, etc. The surface of the uppermost particle layer is loaded by the ram 6 of a press in order to avoid a decomposition during the vibration process, whereby this ram is constantly under pressure even when the fill level decreases due to the compression of the particles caused by the vibration. One recognizes that the particles of the single fractions must travel only small distances in order to arrive in the hollow spaces of the next coarser fraction and to fill out same. In this manner it is possible to produce a quasi-homogeneous formation not only with a ball-shaped particles but also with particles which have adges.

According to FIG. 2, the container 1 is also arranged on a vibrator 2 and the uppermost layer of particles is loaded by the ram 6 of a press during vibration. Ditfering from the filling manner of the particles according to FIG. 1, here, the partial amounts of fractions 3 and 4 are mixed together before lling and on top of these mixed partial amounts there is lled a partial amount of the fraction 5, whereby again rall fractions are divided into four partial amounts.

In case of a larger number of fractions of different sizes, other combinations of single partial amounts are of course also possible through a preceding mixing. It is also possible to do the successive lling diiferently than according to the sequence of decreasing size.

Generally speaking it is at first necessary in each of the examples for the manufacture of a formation of a certain geometry to calculate the individual weight of the coarse, medium and fine fractions. In lling the container, the structure and nature permit determination of the layer height. Based on the thus found layer height, the number of divisions of each fraction can be determined for a specific requested total length or height of the formation. These partial amounts are then weighed and lfilled which can for example be done by an automatic scale. It is desired to keep the vibration time short which leads to a specific number of divisions in a given container size.

Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

The embodiments of the invention in which I claim an exclusive property or privilege are defined as follows:

1. A process for the formation of a quasi-homogeneous mass of separate particles o.f different particle size within a container and usable with rounded and broken edged particles, comprising the steps of:

(1) providing a quantity of separate particles or different size which together are required for the forma- 4 tion of a mass having a predetermined volume when disposed within said container;

(2) dividing said quantity of particles into a plurality of fractions according to particles size with the `amount of each fraction being selected to that when the particles are within the container the next smaller particles as contained in one fraction will fill out the hollow space between the next larger particles as contained in -a further fraction;

(3) subdividing said fractions into the same number of partial amounts;

(4) successively depositing a partial amount of each fraction into said container to form a layer-like sequence of decreasing particle size;

(5) repeating step (4) above for the remaining partial amounts to cause further layer-like sequences of decreasing particle size to be deposited on top of said first-mentioned layer-like sequence; then pressurizing by use of a ram under continued pressure the uppermost particle layer; and

vibrating said container for causing the smaller particles to enter into the spaces between the larger particles so that a quasi-homogeneous formation is created within said container.

2. A method according to claim 1, wherein mixed partial amounts of different fractions are deposited into the container interchangeably with a partial amount of a further .fraction, and the sequence is repeated according to .the number of divisions of each fraction.

References Cited UNITED STATES PATENTS 3,102,850 9/ 1963 Ross et al 264-0.5 3,517,431 6/ 1970 Ayer 264-0.5 X 3,230,280 1/ 1966 Kennedy 264-0.5 3,293,332 12/ 1966 Ingleby 264-0.5 3,413,383 11/ 1968 Hirose et al 264-0.5

CARL D. QUARFORTH, Primary Examiner R. S. GAITHER, Assistant Examiner U.S. Cl. X.R. 264-69 

